This ASM message is used by the ASM shore station to broadcast FATDMA reservations. It should be repeated as often as required. Link ID 5 should always be used.
The mobile station, within 120 nautical miles should then reserve the slots as unavailable for its own transmission until time‑out occurs. The shore station should refresh the time-out value with each transmission of Message 7 in order to allow mobile stations to terminate their reservation for the use of the slots.
The parameters: offset number, number of slots, time-out, and increment should be treated as a unit, meaning that if one parameter is defined all other parameters should be defined within that unit. The parameter offset number should denote the offset from the slot in which Message 7 was received to the first slot to be reserved. The parameter number of slots should denote the number of consecutive slots to be reserved starting with the first reserved slot. This defines a reservation block.
This reservation block should not exceed 15 slots. The parameter increment should denote the number of slots between the starting slot of each reservation block. An increment of zero indicates one reservation block per frame. The following values for increment are allowed: 30, 45, 50, 75, 90, 125, 150, 225, 250, 375, 450, 750 or 1 125. Use of one of these values guarantees symmetric slot reservations throughout each frame. ASM data link management message is described in Table 33.
Table 33
ASM data link management message
|
Reservation Block |
Parameter |
Number of bits |
Description |
|---|---|---|---|
|
|
Message ID |
4 |
7 – ASM Data link management. |
|
Retransmit flag |
1 |
0 (reserved for future use). |
|
|
Repeat indicator |
2 |
Used by the repeater to indicate how many times a message has been repeated. |
|
|
Session ID |
6 |
The Session ID associates the VDL transmission with a specific PI transaction. |
|
|
Source ID |
32 |
The Unique Identifier of the transmitting station as described in |
|
|
Reservation Block 1 |
Channel selection |
2 |
0 = ASM1; 1 = ASM2; 2 = ASM1 and ASM2; 3 = no reservation. |
|
Offset number |
12 |
Reserved offset number. |
|
|
Number of slots |
4 |
Number of reserved consecutive slots: 1-15. |
|
|
Time-out |
4 |
Time-out value in minutes. |
|
|
Increment |
4 |
Increment to repeat reservation block 1. 0 = one reservation block per frame. 1 = 30, 2 = 45, 3 = 50, 4 = 75, 5 = 90, 6 = 125, 7 = 150, 8 = 225, 9 = 250, 10 = 375, 11 = 450, 12 = 750, 13 = 1125, 14-15 not used |
|
Reservation Block 2 |
Channel selection |
2 |
0 = ASM1; 1 = ASM2; 2 = ASM1 and ASM2; 3 = no reservation. |
|
Offset number |
12 |
Reserved offset number. |
|
|
Number of slots |
4 |
Number of reserved consecutive slots: 1-15. |
|
|
Time-out |
4 |
Time-out value in minutes. |
|
|
Increment |
4 |
Increment to repeat reservation block 2. 0 = one reservation block per frame. 1 = 30, 2 = 45, 3 = 50, 4 = 75, 5 = 90, 6 = 125, 7 = 150, 8 = 225, 9 = 250, 10 = 375, 11 = 450, 12 = 750, 13 = 1125, 14-15 not used. |
|
|
Reservation Block 3 |
Channel selection |
2 |
0 = ASM1; 1 = ASM2; 2 = ASM1 and ASM2; 3 = no reservation. |
|
Offset number |
12 |
Reserved offset number. |
|
|
Number of slots |
4 |
Number of reserved consecutive slots: 1-15. |
|
|
Time-out |
4 |
Time-out value in minutes. |
|
|
Increment |
4 |
Increment to repeat reservation block 3. 0 = one reservation block per frame. 1 = 30, 2 = 45, 3 = 50, 4 = 75, 5 = 90, 6 = 125, 7 = 150, 8 = 225, 9 = 250, 10 = 375, 11 = 450, 12 = 750, 13 = 1125, 14-15 not used. |
|
|
Reservation Block 4 |
Channel selection |
2 |
0 = ASM1; 1 = ASM2; 2 = ASM1 and ASM2; 3 = no reservation. |
|
Offset number |
12 |
Reserved offset number. |
|
|
Number of slots |
4 |
Number of reserved consecutive slots: 1-15. |
|
|
Time-out |
4 |
Time-out value in minutes. |
|
|
Increment |
4 |
Increment to repeat reservation block 4. 0 = one reservation block per frame. 1 = 30, 2 = 45, 3 = 50, 4 = 75, 5 = 90, 6 = 125, 7 = 150, 8 = 225, 9 = 250, 10 = 375, 11 = 450, 12 = 750, 13 = 1125, 14-15 not used. |
|
Reservation Block 5 |
Channel selection |
2 |
0 = ASM1; 1 = ASM2; 2 = ASM1 and ASM2; 3 = no reservation. |
|
Offset number |
12 |
Reserved offset number. |
|
|
Number of slots |
4 |
Number of reserved consecutive slots: 1-15. |
|
|
Time-out |
4 |
Time-out value in minutes. |
|
|
Increment |
4 |
Increment to repeat reservation block 5. 0 = one reservation block per frame. 1 = 30, 2 = 45, 3 = 50, 4 = 75, 5 = 90, 6 = 125, 7 = 150, 8 = 225, 9 = 250, 10 = 375, 11 = 450, 12 = 750, 13 = 1125, 14-15 not used. |
|
|
Reservation Block 6 |
Channel selection |
2 |
0 = ASM1; 1 = ASM2; 2 = ASM1 and ASM2; 3 = no reservation. |
|
Offset number |
12 |
Reserved offset number. |
|
|
Number of slots |
4 |
Number of reserved consecutive slots: 1-15. |
|
|
Time-out |
4 |
Time-out value in minutes. |
|
|
Increment |
4 |
Increment to repeat reservation block 6. 0 = one reservation block per frame. 1 = 30, 2 = 45, 3 = 50, 4 = 75, 5 = 90, 6 = 125, 7 = 150, 8 = 225, 9 = 250, 10 = 375, 11 = 450, 12 = 750, 13 = 1125, 14-15 not used. |
|
|
Reservation Block 7 |
Channel selection |
2 |
0 = ASM1; 1 = ASM2; 2 = ASM1 and ASM2; 3 = no reservation. |
|
Offset number |
12 |
Reserved offset number. |
|
|
Number of slots |
4 |
Number of reserved consecutive slots: 1-15. |
|
|
Time-out |
4 |
Time-out value in minutes. |
|
|
Increment |
4 |
Increment to repeat reservation block 7. 0 = one reservation block per frame. 1 = 30, 2 = 45, 3 = 50, 4 = 75, 5 = 90, 6 = 125, 7 = 150, 8 = 225, 9 = 250, 10 = 375, 11 = 450, 12 = 750, 13 = 1125, 14-15 not used. |
|
Reservation Block 8 |
Channel selection |
2 |
0 = ASM1; 1 = ASM2; 2 = ASM1 and ASM2; 3 = no reservation. |
|
Offset number |
12 |
Reserved offset number. |
|
|
Number of slots |
4 |
Number of reserved consecutive slots: 1-15. |
|
|
Time-out |
4 |
Time-out value in minutes. |
|
|
Increment |
4 |
Increment to repeat reservation block 8. 0 = one reservation block per frame. 1 = 30, 2 = 45, 3 = 50, 4 = 75, 5 = 90, 6 = 125, 7 = 150, 8 = 225, 9 = 250, 10 = 375, 11 = 450, 12 = 750, 13 = 1125, 14-15 not used. |
|
|
|
Spare |
3 |
Spare bits – reserved for the future. |